311 lines
12 KiB
C
311 lines
12 KiB
C
#ifndef __NET_NSH_H
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#define __NET_NSH_H 1
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#include <linux/skbuff.h>
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/*
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* Network Service Header:
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* 0 1 2 3
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* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* |Ver|O|U| TTL | Length |U|U|U|U|MD Type| Next Protocol |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | Service Path Identifier (SPI) | Service Index |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | |
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* ~ Mandatory/Optional Context Headers ~
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* | |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*
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* Version: The version field is used to ensure backward compatibility
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* going forward with future NSH specification updates. It MUST be set
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* to 0x0 by the sender, in this first revision of NSH. Given the
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* widespread implementation of existing hardware that uses the first
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* nibble after an MPLS label stack for ECMP decision processing, this
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* document reserves version 01b and this value MUST NOT be used in
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* future versions of the protocol. Please see [RFC7325] for further
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* discussion of MPLS-related forwarding requirements.
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*
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* O bit: Setting this bit indicates an Operations, Administration, and
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* Maintenance (OAM) packet. The actual format and processing of SFC
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* OAM packets is outside the scope of this specification (see for
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* example [I-D.ietf-sfc-oam-framework] for one approach).
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*
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* The O bit MUST be set for OAM packets and MUST NOT be set for non-OAM
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* packets. The O bit MUST NOT be modified along the SFP.
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*
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* SF/SFF/SFC Proxy/Classifier implementations that do not support SFC
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* OAM procedures SHOULD discard packets with O bit set, but MAY support
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* a configurable parameter to enable forwarding received SFC OAM
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* packets unmodified to the next element in the chain. Forwarding OAM
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* packets unmodified by SFC elements that do not support SFC OAM
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* procedures may be acceptable for a subset of OAM functions, but can
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* result in unexpected outcomes for others, thus it is recommended to
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* analyze the impact of forwarding an OAM packet for all OAM functions
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* prior to enabling this behavior. The configurable parameter MUST be
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* disabled by default.
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*
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* TTL: Indicates the maximum SFF hops for an SFP. This field is used
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* for service plane loop detection. The initial TTL value SHOULD be
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* configurable via the control plane; the configured initial value can
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* be specific to one or more SFPs. If no initial value is explicitly
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* provided, the default initial TTL value of 63 MUST be used. Each SFF
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* involved in forwarding an NSH packet MUST decrement the TTL value by
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* 1 prior to NSH forwarding lookup. Decrementing by 1 from an incoming
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* value of 0 shall result in a TTL value of 63. The packet MUST NOT be
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* forwarded if TTL is, after decrement, 0.
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*
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* All other flag fields, marked U, are unassigned and available for
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* future use, see Section 11.2.1. Unassigned bits MUST be set to zero
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* upon origination, and MUST be ignored and preserved unmodified by
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* other NSH supporting elements. Elements which do not understand the
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* meaning of any of these bits MUST NOT modify their actions based on
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* those unknown bits.
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*
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* Length: The total length, in 4-byte words, of NSH including the Base
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* Header, the Service Path Header, the Fixed Length Context Header or
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* Variable Length Context Header(s). The length MUST be 0x6 for MD
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* Type equal to 0x1, and MUST be 0x2 or greater for MD Type equal to
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* 0x2. The length of the NSH header MUST be an integer multiple of 4
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* bytes, thus variable length metadata is always padded out to a
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* multiple of 4 bytes.
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*
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* MD Type: Indicates the format of NSH beyond the mandatory Base Header
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* and the Service Path Header. MD Type defines the format of the
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* metadata being carried.
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*
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* 0x0 - This is a reserved value. Implementations SHOULD silently
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* discard packets with MD Type 0x0.
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*
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* 0x1 - This indicates that the format of the header includes a fixed
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* length Context Header (see Figure 4 below).
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*
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* 0x2 - This does not mandate any headers beyond the Base Header and
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* Service Path Header, but may contain optional variable length Context
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* Header(s). The semantics of the variable length Context Header(s)
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* are not defined in this document. The format of the optional
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* variable length Context Headers is provided in Section 2.5.1.
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*
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* 0xF - This value is reserved for experimentation and testing, as per
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* [RFC3692]. Implementations not explicitly configured to be part of
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* an experiment SHOULD silently discard packets with MD Type 0xF.
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*
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* Next Protocol: indicates the protocol type of the encapsulated data.
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* NSH does not alter the inner payload, and the semantics on the inner
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* protocol remain unchanged due to NSH service function chaining.
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* Please see the IANA Considerations section below, Section 11.2.5.
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*
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* This document defines the following Next Protocol values:
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*
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* 0x1: IPv4
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* 0x2: IPv6
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* 0x3: Ethernet
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* 0x4: NSH
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* 0x5: MPLS
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* 0xFE: Experiment 1
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* 0xFF: Experiment 2
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*
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* Packets with Next Protocol values not supported SHOULD be silently
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* dropped by default, although an implementation MAY provide a
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* configuration parameter to forward them. Additionally, an
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* implementation not explicitly configured for a specific experiment
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* [RFC3692] SHOULD silently drop packets with Next Protocol values 0xFE
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* and 0xFF.
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*
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* Service Path Identifier (SPI): Identifies a service path.
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* Participating nodes MUST use this identifier for Service Function
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* Path selection. The initial classifier MUST set the appropriate SPI
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* for a given classification result.
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*
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* Service Index (SI): Provides location within the SFP. The initial
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* classifier for a given SFP SHOULD set the SI to 255, however the
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* control plane MAY configure the initial value of SI as appropriate
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* (i.e., taking into account the length of the service function path).
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* The Service Index MUST be decremented by a value of 1 by Service
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* Functions or by SFC Proxy nodes after performing required services
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* and the new decremented SI value MUST be used in the egress packet's
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* NSH. The initial Classifier MUST send the packet to the first SFF in
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* the identified SFP for forwarding along an SFP. If re-classification
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* occurs, and that re-classification results in a new SPI, the
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* (re)classifier is, in effect, the initial classifier for the
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* resultant SPI.
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*
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* The SI is used in conjunction the with Service Path Identifier for
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* Service Function Path Selection and for determining the next SFF/SF
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* in the path. The SI is also valuable when troubleshooting or
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* reporting service paths. Additionally, while the TTL field is the
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* main mechanism for service plane loop detection, the SI can also be
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* used for detecting service plane loops.
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*
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* When the Base Header specifies MD Type = 0x1, a Fixed Length Context
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* Header (16-bytes) MUST be present immediately following the Service
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* Path Header. The value of a Fixed Length Context
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* Header that carries no metadata MUST be set to zero.
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*
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* When the base header specifies MD Type = 0x2, zero or more Variable
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* Length Context Headers MAY be added, immediately following the
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* Service Path Header (see Figure 5). Therefore, Length = 0x2,
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* indicates that only the Base Header followed by the Service Path
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* Header are present. The optional Variable Length Context Headers
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* MUST be of an integer number of 4-bytes. The base header Length
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* field MUST be used to determine the offset to locate the original
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* packet or frame for SFC nodes that require access to that
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* information.
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*
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* The format of the optional variable length Context Headers
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*
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* 0 1 2 3
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* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | Metadata Class | Type |U| Length |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* | Variable Metadata |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*
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* Metadata Class (MD Class): Defines the scope of the 'Type' field to
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* provide a hierarchical namespace. The IANA Considerations
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* Section 11.2.4 defines how the MD Class values can be allocated to
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* standards bodies, vendors, and others.
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*
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* Type: Indicates the explicit type of metadata being carried. The
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* definition of the Type is the responsibility of the MD Class owner.
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*
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* Unassigned bit: One unassigned bit is available for future use. This
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* bit MUST NOT be set, and MUST be ignored on receipt.
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*
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* Length: Indicates the length of the variable metadata, in bytes. In
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* case the metadata length is not an integer number of 4-byte words,
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* the sender MUST add pad bytes immediately following the last metadata
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* byte to extend the metadata to an integer number of 4-byte words.
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* The receiver MUST round up the length field to the nearest 4-byte
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* word boundary, to locate and process the next field in the packet.
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* The receiver MUST access only those bytes in the metadata indicated
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* by the length field (i.e., actual number of bytes) and MUST ignore
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* the remaining bytes up to the nearest 4-byte word boundary. The
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* Length may be 0 or greater.
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*
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* A value of 0 denotes a Context Header without a Variable Metadata
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* field.
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*
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* [0] https://datatracker.ietf.org/doc/draft-ietf-sfc-nsh/
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*/
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/**
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* struct nsh_md1_ctx - Keeps track of NSH context data
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* @nshc<1-4>: NSH Contexts.
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*/
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struct nsh_md1_ctx {
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__be32 context[4];
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};
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struct nsh_md2_tlv {
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__be16 md_class;
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u8 type;
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u8 length;
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u8 md_value[];
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};
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struct nshhdr {
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__be16 ver_flags_ttl_len;
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u8 mdtype;
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u8 np;
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__be32 path_hdr;
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union {
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struct nsh_md1_ctx md1;
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struct nsh_md2_tlv md2;
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};
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};
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/* Masking NSH header fields. */
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#define NSH_VER_MASK 0xc000
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#define NSH_VER_SHIFT 14
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#define NSH_FLAGS_MASK 0x3000
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#define NSH_FLAGS_SHIFT 12
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#define NSH_TTL_MASK 0x0fc0
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#define NSH_TTL_SHIFT 6
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#define NSH_LEN_MASK 0x003f
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#define NSH_LEN_SHIFT 0
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#define NSH_MDTYPE_MASK 0x0f
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#define NSH_MDTYPE_SHIFT 0
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#define NSH_SPI_MASK 0xffffff00
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#define NSH_SPI_SHIFT 8
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#define NSH_SI_MASK 0x000000ff
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#define NSH_SI_SHIFT 0
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/* MD Type Registry. */
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#define NSH_M_TYPE1 0x01
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#define NSH_M_TYPE2 0x02
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#define NSH_M_EXP1 0xFE
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#define NSH_M_EXP2 0xFF
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/* NSH Base Header Length */
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#define NSH_BASE_HDR_LEN 8
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/* NSH MD Type 1 header Length. */
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#define NSH_M_TYPE1_LEN 24
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/* NSH header maximum Length. */
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#define NSH_HDR_MAX_LEN 256
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/* NSH context headers maximum Length. */
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#define NSH_CTX_HDRS_MAX_LEN 248
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static inline struct nshhdr *nsh_hdr(struct sk_buff *skb)
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{
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return (struct nshhdr *)skb_network_header(skb);
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}
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static inline u16 nsh_hdr_len(const struct nshhdr *nsh)
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{
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return ((ntohs(nsh->ver_flags_ttl_len) & NSH_LEN_MASK)
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>> NSH_LEN_SHIFT) << 2;
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}
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static inline u8 nsh_get_ver(const struct nshhdr *nsh)
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{
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return (ntohs(nsh->ver_flags_ttl_len) & NSH_VER_MASK)
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>> NSH_VER_SHIFT;
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}
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static inline u8 nsh_get_flags(const struct nshhdr *nsh)
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{
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return (ntohs(nsh->ver_flags_ttl_len) & NSH_FLAGS_MASK)
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>> NSH_FLAGS_SHIFT;
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}
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static inline u8 nsh_get_ttl(const struct nshhdr *nsh)
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{
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return (ntohs(nsh->ver_flags_ttl_len) & NSH_TTL_MASK)
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>> NSH_TTL_SHIFT;
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}
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static inline void __nsh_set_xflag(struct nshhdr *nsh, u16 xflag, u16 xmask)
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{
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nsh->ver_flags_ttl_len
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= (nsh->ver_flags_ttl_len & ~htons(xmask)) | htons(xflag);
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}
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static inline void nsh_set_flags_and_ttl(struct nshhdr *nsh, u8 flags, u8 ttl)
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{
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__nsh_set_xflag(nsh, ((flags << NSH_FLAGS_SHIFT) & NSH_FLAGS_MASK) |
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((ttl << NSH_TTL_SHIFT) & NSH_TTL_MASK),
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NSH_FLAGS_MASK | NSH_TTL_MASK);
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}
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static inline void nsh_set_flags_ttl_len(struct nshhdr *nsh, u8 flags,
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u8 ttl, u8 len)
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{
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len = len >> 2;
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__nsh_set_xflag(nsh, ((flags << NSH_FLAGS_SHIFT) & NSH_FLAGS_MASK) |
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((ttl << NSH_TTL_SHIFT) & NSH_TTL_MASK) |
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((len << NSH_LEN_SHIFT) & NSH_LEN_MASK),
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NSH_FLAGS_MASK | NSH_TTL_MASK | NSH_LEN_MASK);
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}
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int nsh_push(struct sk_buff *skb, const struct nshhdr *pushed_nh);
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int nsh_pop(struct sk_buff *skb);
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#endif /* __NET_NSH_H */
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